Nonaqueous electrolyte battery

ABSTRACT

A nonaqueous electrolyte battery which comprises a positive electrode including carbon fluoride or sulfur as an active material, a negative electrode including calcium as an active material, and an electrolyte including an imide salt of calcium or a sulfonic acid salt of calcium.

This application is a division of U.S. patent application Ser. No.10/786,594 filed Feb. 26, 2004, which claims priority of Japanese PatentApplication Nos. 2003-53550 and 2003-67157 filed Feb. 28 and Mar. 12,2003, respectively, each of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a nonaqueous electrolyte battery, andmore specifically, to a nonaqueous electrolyte battery using calcium asits active material.

2. Description of the Related Art

Conventionally, in researches for secondary batteries with high energydensity, nonaqueous electrolyte secondary batteries which use anonaqueous electrolyte and make lithium ions transfer between a positiveelectrode and a negative electrode to achieve charge/discharge have beenvigorously studied.

In recent years, as batteries to be used in portableelectronic/communicative equipments such as small-sized video camera,portable phone, laptop and the like, nonaqueous electrolyte batteriesrepresented by a lithium-ion battery are expected for practical use asbatteries which are small in size and weight and enable charge/dischargewith a large capacity. A commonly used lithium-ion battery uses analloy, a carbon or silicon material capable of absorbing, storing anddischarging lithium ions, or the like as a negative electrode activematerial, layer-shaped lithium cobalt (LiCoO₂), lithium transition metalcomplex oxides such as lithium nickel oxide (LiNiO₂), spinel-shapedlithium manganese oxide (LiMn₂O₄) as a positive electrode activematerial, and a solution of electrolyte comprising lithium salts such asLiBF₄ and LiPF₆ dissolved in an organic solvent such as ethylenecarbonate and diethyl carbonate.

Also proposed is a battery which uses carbon fluoride as a positiveelectrode active material, a negative electrode formed of an alkalinemetal such as lithium and sodium, and a nonaqueous electrolyte (seeJapanese Patent Publication No. 48-25566).

Also proposed is a battery which uses sulfur as a positive electrodeactive material, a negative electrode formed of an alkaline metal suchas lithium, sodium and the like, and a nonaqueous electrolyte (seeJapanese Patent Publication Laid Open 2002-75446).

On the other hand, from the view point of energy density, researches aremade in which alkaline earth metals such as magnesium and calcium orlight metals such as aluminum are used as a negative electrode activematerial.

When calcium ions are used as an ion conductive medium in place oflithium ions, there arises an advantage that the number of reactiveelectrons is large and the cost is inexpensive.

Although batteries using such calcium ions as an active material havebeen suggested, any of the batteries using calcium ions as an activematerial that have been reported and practically used employ sulfides oroxides for a positive electrode and have a capacity of as small as 200mAh/g or less.

Furthermore, batteries that are practically used and employ calcium ionsas an active material used perchlorates such as calcium perchlorate(Ca(ClO₄)₂) as an electrolyte.

However, since calcium perchlorate is a salt of peroxide, and hencechemically unstable and likely to release oxygen, it is too risky to beactually used as an electrolyte. Therefore, a nonaqueous electrolytebattery using such a peroxide salt of calcium as an electrolyte couldnot bear practical use.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a nonaqueouselectrolyte battery having a large capacity and excellent safety.

In a first aspect of the present invention, a nonaqueous electrolytebattery comprises a positive electrode including carbon fluoride as anactive material, a negative electrode including calcium as an activematerial, and an electrolyte including an imide salt of calcium or asulfonic acid salt of calcium.

According to such a configuration, since an imide salt of calcium or asulfonic acid salt of calcium which is chemically stable rather thanperoxides is used as an electrolyte, it is possible to provide anonaqueous electrolyte battery having a large capacity and realizinggreater safety. The nonaqueous electrolyte is preferably in the statethat an imide salt of calcium or a sulfonic acid salt of calcium isdissolved in an organic solvent, however, it may be in a solidelectrolyte state formed of an imide salt of calcium or a sulfonic acidsalt of calcium.

The oxidation-reduction potential of calcium ion is as low as −2.866Vrelative to the normal hydrogen electrode (NHE) as shown below. Since 2moles of electrons will move for oxidizing or reducing 1 mole of Caions, Ca ions are ionic species that are expected to give high energydensity.Ca²⁺⁺2^(e−)

Ca−2.866 vs. NHE

Carbon fluorides that are used as an active material will be, if C_(x)F(x=1 to 9) are used, an active material of a positive electrode of alarge capacity in which usability of the active material is high and thepotential has an excellent flatness. For example, if CF (x=1) is usedfor a positive electrode, the battery having a large capacity of about865 mAh/g based on a theoretical capacity density can be expected.

Also, the nonaqueous electrolyte battery of the present inventionincludes such a battery wherein the electrolyte includes a sulfonylimide salt of calcium, thereby realizing a safe and a large capacitybattery.

Preferably, the sulfonyl imide salt of calcium is an alkylsulfonyl imidesalt of calcium.

Preferably, the alkylsulfonyl imide salt of calcium includes at leastone selected from the group consisting of Ca[N(CF₃SO₂)₂]₂,Ca[N(C₂F₅SO₂)₂.]₂, Ca[(C₄F₉SO₂)(CF₃SO₂)N]₂, Ca[(C₆F₅SO₂)(CF₃SO₂)N]₂,Ca[(C₈F₁₇SO₂)(CF₃SO₂)N]₂, Ca[N(CF₃CH₂OSO₂)₂]₂, Ca[N(CF₃CF₂CH₂OSO₂)₂]₂and Ca[N(CF₃)₂CHOSO₂)₂]₂.

Furthermore, as the electrolyte, those including calciumbis(trifluoromethylsulfonyl)imide, Ca[N(CF₃SO₂)₂]₂ are particularlypreferred.

Furthermore, as the above sulfonic acid salt, alkylsulfonic acid saltsare preferred.

Furthermore, as these alkylsulfonic acid salts, those including at leastone selected from the group consisting of Ca(CF₃SO₃)₂, Ca(CH₃SO₃)₂,Ca(C₄F₉SO₃)₂, Ca (C₆F₅SO₃)₂ and Ca(C₈F₁₇SO₃)₂ are particularlypreferred.

Furthermore, as the electrolyte, those including calciumtrifluoromethanesulfonate, Ca(CF₃SO₃)₂ are more preferred.

In this context, imide salts or sulfonic acid salts of calcium may beused solely or in combination of two or more kinds. The electrolyte isdissolved in an organic solvent in a final concentration of 0.1 to 1.5M, preferably 0.5 to 1.5 M for use.

Test results have showed that these concentrations provide batterieswith stability and a large capacity.

In a second aspect of the present invention, the nonaqueous electrolytebattery comprises a positive electrode including sulfur as an activematerial, a negative electrode including calcium as an active material,and a nonaqueous electrolyte including a calcium salt.

Sulfur used as an active material has a large theoretical capacity of ashigh as 742 mAh/g when combined with calcium, and hence high energydensity can be expected.

The material constituting the positive electrode may have anycomposition insofar as it contains sulfur in even a small amount.However, since sulfur does not have a sufficient conductivity, forimproving the charge/discharge characteristics by increasing theconductivity, it is preferred to add a conductive agent to the positiveelectrode. As such a conductive agent, for example, conductive carbonmaterials or the like can be exemplified. It is to be noted that inadding such a conductive carbon material, if the adding amount is toosmall, it will not be possible to satisfactorily improve theconductivity at the positive electrode. Contrarily, if the adding amountis too large, the proportion of sulfur at the positive electrode willbecome too small to realize a large capacity. For this reason, in usinga carbon material as a conductive agent, the carbon material is added sothat it occupies 5 to 84% by mass, preferably 5 to 54% by mass, morepreferably 5 to 20% by mass, relative to the total content of thepositive electrode.

Preferably, the calcium salt includes at least one of imide salts andsulfonic acid salts.

Since imide salts and sulfonic acid salts are more stable and lessliable to release oxygen than calcium perchlorate, they are safe as anelectrolyte and can provide a nonaqueous electrolyte battery having highsafety and a large capacity.

Although the nonaqueous electrolyte is preferably in such a state thatan imide salt of calcium or a sulfonic acid salt of calcium is dissolvedin an organic solvent (electrolyte solution) or in such a state that asalt which melts at room temperature is added to the electrolytesolution, the electrolyte may be a solid electrolyte including an imidesalt of calcium or a sulfonic acid salt of calcium.

In addition, the electrolyte preferably includes a sulfonyl imide saltof calcium, whereby a battery of safety and a large capacity isrealized.

As the sulfonyl imide salt of calcium, alkylsulfonyl imide salts ofcalcium are preferred.

Preferably, the alkylsulfonyl imide salt of calcium includes at leastone selected from the group consisting of Ca[N(CF₃SO₂)₂]₂,Ca[N(C₂F₅SO₂)₂]₂, Ca[(C₄F₉SO₂)(CF₃SO₂)N]₂, Ca[(C₆F₅SO₂)(CF₃SO₂)N]₂,Ca[(C₈F₁₇SO₂)(CF₃SO₂)N]₂, Ca[N(CF₃CH₂OSO₂)₂]₂, Ca[N(CF₃CF₂CH₂OSO₂)₂]₂and Ca[N(CF₃)₂CHOSO₂)₂]₂.

Furthermore, as the electrolyte, those including calciumbis(trifluoromethylsulfonyl)imide, Ca[N(CF₃SO₂)₂]₂ are particularlypreferred.

Furthermore, as the above sulfonic acid salt, alkylsulfonic acid saltsare preferred.

Furthermore, as these alkylsulfonic acid salts, those including at leastone selected from the group consisting of Ca(CF₃SO₃)₂, Ca(CH₃SO₃)₂,Ca(C₄F₉SO₃)₂, Ca(C₆F₅SO₃)₂ and Ca(C₈F₁₇SO₃)₂ are preferred.

Furthermore, as the electrolyte, those including calciumtrifluoromethanesulfonate, Ca(CF₃SO₃)₂ are more preferred.

In this context, imide salts or sulfonic acid salts of calcium may beused solely or in combination of two or more kinds. The electrolyte isdissolved in an organic solvent in a final concentration of 0.1 to 1.5M, preferably 0.5 to 1.5 M for use.

Test results have showed that these concentrations provide batterieswith stability and a large capacity.

Examples of the organic solvent (nonaqueous solvent) used for thenonaqueous electrolyte include esters such as cyclic esters, cycliccarbonic acid esters and chain carbonic acid esters, cyclic ethers,chain ethers, nitriles, amides and the like. Examples of the cycliccarbonic acid esters include ethylene-carbonate ((CH₂)₂O₂CO), propylenecarbonate (CH₃CHCH₂O₂CO), butylene carbonate (CH₃CH₂CHCH₂O₂CO) and thelike, as well as those derived by fluorinating part or whole of hydrogenof the above compounds, such as trifluoropropylene carbonate(CF₃CHCH₂O₂CO). Examples of the chain carbonic acid esters includedimethyl carbonate ((CH₃O)₂CO), ethylmethyl carbonate((CH₃O)(C₂H₅O)CO)), diethyl carbonate ((C₂H₅O)₂CO), methylpropylcarbonate ((CH₃O)(C₃H₇O)CO), ethylpropyl carbonate ((C₂H₅O)(C₃H₇O)CO)methylisopropyl carbonate ((CH₃O)((CH₃)₂CHO)CO) and the like, as well asthose derived by fluorinating part or whole of hydrogen of the abovecompounds. Examples of the esters include methyl acetate (CH₃COOCH₃),ethyl acetate (CH₃COOC₂H₅), propyl acetate (CH₃COOC₃H₇), methylpropionate (C₂H₅COOCH₃), ethyl propionate (C₂H₅COOC₂H₅), γ-butyrolactone((CH₂)₃OCO) and the like. Examples of the cyclic ethers include1,3-dioxirane ((CH₂)₃O₂), 4-methyl-1,3-dioxirane (CH₃CH(CH₂)₂O₂),tetrahydrofuran ((CH₂)₄O), 2-methyltetrahydrofuran (CH₃CH(CH₂)₃O),propylene oxide (CH₃CHCH₂O), 1,2-butylene oxide (CH₃CH₂CHCH₂O),1,4-dioxane ((CH₂)₄O₂), 1,3,5-trioaxane ((CH₂)₃O₃), furan ((CH)₄O),2-methylfuran ((CH)₃CCH₃O), 1,8-cineole (CH₃CO((CH₂)₄CH)C(CH₃)₂), crownether and the like. Examples of the chain ethers include 1,2-dimethoxyethane ((CH₃O)₂(CH₂)₂), diethyl ether ((C₂H₅) 20), dipropyl ether((C₃H₇) 20), diisopropyl ether (((CH₃)₂CH)₂O), dibutyl ether ((C₄H₉)₂O),dihexyl ether ((C₆H₁₃)₂O), ethylvinyl ether (CH₂CHOC₂H₅), butylvinylether (CH₂CHOC₄H₉), methylphenyl ether (C₆H₅OCH₃), ethylphenyl ether(C₆H₅OC₂H₅), buthylphenyl ether (C₆H₅OC₄H₉), pentylphenyl ether(C₆H₅OC₅H₁₁) methoxytoluene ((CH₃)C₆H₄OCH₃), benzylethyl ether(C₆H₅CH₂OC₂H₅), diphenyl ether ((C₆H₅)₂O), dibenzyl ether ((C₆H₅CH₂)₂O),o-dimethoxy benzene (C₆H₄ (OCH₃)₂), 1,2-diethoxy ethane((C₂H₅O)₂(CH₂)₂), 1,2-dibutoxy ethane ((C₄H₉O)₂(CH₂)₂) diethyleneglycoldimethylether ((C₃H₇O)₂O), diethyleneglycol diethylether((C₂H₅OC₂H₄)₂O), diethyleneglycol dibutylether ((C₄H₉OC₂H₄)₂O),1,1-dimethoxyethane ((CH₃O)₂CH₂), 1,1-diethoxyethane ((C₂H₅O)₂CHCH₃),triethyleneglycol dimethylether ((CH₃)₂(C₂H₄O)₃), tetraethyleneglycoldimethylether ((CH₃)₂(C₂H₄O)₄) and the like. Examples of the nitrilesinclude acetonitrile (CH₃CN), and examples of the amides includedimethylformamide (HCON(CH₃)₂) and the like. Mixed solvents of two ormore kinds as recited above may be usable.

Still more, the nonaqueous electrolyte preferably includes a salt asmentioned below which melts at room temperature (also referred to as“room-temperature melting salt”) having a melting point of not more than60° C. Preferably, the room-temperature melting salt includes at leastone selected from the group consisting of: trimethyl propyl ammoniumbis(trifluoromethylsulfonyl)imide ((CH₃)₃N⁺(C₃H₇)N⁻(SO₂CF₃)₂), trimethyloctyl ammonium bis(trifluoromethylsulfonyl)imide((CH₃)₃N⁺(C₈H₁₇)N⁻(SO₂CF₃)₂), trimethyl allyl ammoniumbis(trifluoromethylsulfonyl)imide ((CH₃)₃N⁺(Allyl)N⁻(SO₂CF₃)₂),trimethyl hexyl ammonium bis(trifluoromethylsulfonyl)imide((CH₃)₃N⁺(C₆H₁₃)N⁻(SO₂CF₃)₂), trimethyl ethyl ammonium2,2,2-trifluoro-N-(trifluoromethylsulfonyl)acetamide((CH₃)₃N⁺(C₂H₅)(CF₃CO)N⁻(SO₂CF₃)), trimethyl allyl ammonium2,2,2-trifluoro-N-(trifluoromethylsulfonyl)acetamide ((CH₃)₃N⁺(Allyl)(CF₃CO)N⁻(SO₂CF₃)), trimethyl propyl ammonium2,2,2-trifluoro-N-(trifluoromethylsulfonyl)acetamide((CH₃)₃N⁺(C₃H₇)(CF₃CO)N⁻(SO₂CF₃)), tetraethyl ammonium2,2,2-trifluoro-N-(trifluoromethylsulfonyl)acetamide((C₂H₅)₄N⁺(CF₃CO)N⁻(SO₂CF₃)), triethylmethyl ammonium2,2,2-trifluoro-N-(trifluoromethylsulfonyl)acetamide((C₂H₅)₄N⁺(CH₃)(CF₃CO)N⁻(SO₂CF₃)), 1-ethyl-3-methylimidazoliumbis(pentafluoroethylsulfonyl)imide ((C₂H₅)(C₃H₃N₂)+(CH₃)N⁻(SO₂C₂F₅)₂),1-ethyl-3-methylimidazolium bis(trifluoroethylsulfonyl)imide((C₂H₅)(C₃H₃N₂)⁺(CH₃)N⁻(SO₂CF₃)₂), 1-ethyl-3-methylimidazoliumtetrafluoroborate ((C₂H₅)(C₃H₃N₂)⁺(CH₃)BF₄ ⁻) and1-ethyl-3-methylimidazolium hexafluoro phosphate((C₂H₅)(C₃H₃N₂)⁺(CH₃)PF₆ ⁻).

As the negative electrode including calcium as an active material,namely, the negative electrode capable of absorbing/discharging calcium,those including at least one of calcium metals, calcium alloys, calciumoxides, silicon, carbon and sulfides of transition metals are preferred.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a test cell of a nonaqueouselectrolyte battery according to Example of the present invention.

FIG. 2 is a view showing a discharge curve of a test cell of Example 1of the present invention.

FIG. 3 is a view showing a discharge curve of a test cell of Example 2of the present invention.

FIG. 4 is a view showing a discharge curve of a test cell of Example 3of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be explained in detailwith reference to the drawings.

First, measurement of conductivity was carried out for a nonaqueouselectrolyte which was prepared by dissolving calciumbis(trifuloromethylsulfonyl)imide, Ca[N(CF₃SO₂)₂]₂ in a mixed solvent(EC:DMC=50:60 (v/v)) of propylene carbonate (PC), γ-butyrolactone (γ-BL)and ethylene carbonate (EC), dimethyl carbonate (DMC). The results areshown in Table 1.

Likewise, measurement of conductivity was carried out for a nonaqueouselectrolyte which was prepared by dissolving calciumtrifluoromethanesulfonate, Ca(CF₃SO₂)₂ in a mixed solvent of propylenecarbonate (PC), γ-butyrolactone (γ-BL), ethylene carbonate (EC) anddimethyl carbonate (DMC).

The results are shown in Table 1. TABLE 1 Conductivity (mS/cm) SaltCa[N(CF₃SO₂)₂]₂ Ca(CF₃SO₃)₂ PC 2.42 2.15 γ-BL 6.55 1.0 EC/DMC 7.59 3.9

These test results show that Ca[N(CF₃SO₂)₂]₂ provides higherconductivity than Ca(CF₃SO₂)₂. Therefore, for the battery of the presentinvention, an imide salt of calcium is more preferable than a sulfonicacid salt of calcium.

EXAMPLE 1

1. Production of Positive Electrode

Carbon fluoride (CF) serving as an active material, carbon serving as aconductive agent, and polyvinylidene fluoride (PVDF) serving as a binderwere mixed in a ratio of 90:5:5 by weight to render a mixed agent, towhich N-methyl-2-pyrrolidone was added to prepare a slurry.

Then this slurry was applied on one side of aluminum foil serving as apositive electrode collector by way of doctor blade method, dried invacuo at 110° C. and evaporated off NMP, thereby forming a positiveelectrode (positive electrode including carbon fluoride as an activematerial).

2. Production of Negative Electrode

A calcium metal plate was cut into a predetermined size so as to producea negative electrode serving as an opposite electrode formed of calciummetal (Ca) (negative electrode including calcium as an active material).

Also a lithium metal plate was cut into a predetermined size so as toprepare a reference electrode formed of lithium metal.

3. Preparation of nonaqueous electrolyte

In trifluoropropylene carbonate solvent, 1 mole/L of calciumbis(trifluoromethylsulfonyl)imide, Ca[N(CF₃SO₂)₂]₂ (imide salt ofcalcium) as an electrolyte was dissolved to prepare a nonaqueouselectrolyte.

4. Production of Test Cell

To a test cell vessel 10 containing a positive electrode 12 a serving asa working electrode which was created by attaching a lead to thepositive electrode that was produced in the manner as described above; anegative electrode 11 serving as an opposite electrode which was createdby attaching a lead to the negative electrode produced in the manner asdescribed above; and a reference electrode 13 produced in the manner asdescribed above, the aforementioned nonaqueous electrolyte 14 waspoured, to thereby produce a test cell as shown in FIG. 1. The referencenumeral 15 denotes a separator.

5. Test

The test cell produced in the manner as described above was subjected toconstant current discharge until the electric potential of the positiveelectrode 12 a relative to the reference electrode 13 at roomtemperature and at a current density of 0.025 mA/cm² became 0.3V (vs.Li/Li⁺).

The discharge curve of this time is shown in FIG. 2. This dischargecurve demonstrates that stable discharge potential is obtainable up toabout 20 mAh/g.

EXAMPLE 2

In Example 2 of the present invention, a nonaqueous electrolyte wasprepared in the same manner as described for Example 1 except that thenonaqueous electrolyte was prepared by dissolving 1 mole/litter ofcalcium bis(trifluoromethylsulfonyl)imide, Ca[N(CF₃SO₂)₂]₂ as anelectrolyte in γ-butyrolactone solvent in place of trifluoropropylenecarbonate.

In other respects, the cell was assembled in the same manner asdescribed for Example 1.

Constant current discharge was carried out until 0.5V with respect tothe electric potential of Li/Li⁺ was reached at a current density of0.025 mA/cm². The resultant discharge curve is shown in FIG. 3. Thisdischarge curve demonstrates that stable discharge potential isobtainable up to about 300 mAh/g.

In the above embodiments, explanation was made for the application to anonaqueous electrolyte battery utilizing a nonaqueous electrolyteprepared by dissolving an electrolyte in a room-temperature melting saltand an organic solvent is used as a nonaqueous electrolyte, it may beapplied to a polymer battery (polymer solid electrolyte battery) using asolid electrolyte.

As described above, according to the first aspect of the invention, itbecomes possible to form a nonaqueous electrolyte battery with safetyand a large capacity by using an electrolyte based on imide or sulfonicacid.

EXAMPLE 3

1. Production of Positive Electrode

50% by mass of sulfur (S) serving as an active material, 45% by mass ofKetjen Black serving as a conductive agent, 4% by mass ofstyrene-butadiene rubber a binder and 1% by mass ofcarboxy-methyl-cellulose as a thickener were mixed to render a mixedagent, to which water was added to prepare a slurry.

Then this slurry was applied on one side of aluminum foil serving as apositive electrode collector by way of doctor blade method, dried invacuo at 50° C. and evaporated off water, thereby forming a positiveelectrode (positive electrode including sulfur as an active material).

2. Production of Negative Electrode

A calcium metal plate was cut into a predetermined size so as to producea negative electrode serving as an opposite electrode formed of calciummetal (Ca) (negative electrode including calcium as an active material).

Also a lithium metal plate was cut into a predetermined size so as toprepare a reference electrode formed of lithium metal.

3. Preparation of Nonaqueous Electrolyte

In γ-butyrolactone ((CH₂)₃OCO), calciumbis(trifluoromethylsulfonyl)imide, Ca[N(CF₃SO₂)₂]₂ was dissolved in aconcentration of 1 mol/L to prepare a nonaqueous electrolyte.

4. Production of Test Cell

To a test cell vessel 10 containing a positive electrode 12 a serving asa working electrode which was created by attaching a lead to thepositive electrode that was produced in the manner as described above; anegative electrode 11 serving as an opposite electrode which was createdby attaching a lead to the negative electrode produced in the manner asdescribed above; and a reference electrode 13 which was created byattaching a lead to the lithium metal produced in the manner asdescribed above, the aforementioned nonaqueous electrolyte 14 waspoured, to thereby produce a test cell as shown in FIG. 1. The referencenumeral 15 denotes a separator.

5. Test

The test cell produced in the manner as described above was subjected toconstant current discharge until 0 V (vs. Li/Li⁺) was reached at roomtemperature and at a current density of 0.025 mA/cm².

The discharge curve of this time is shown in FIG. 4. This dischargecurve demonstrates that sulfur has a discharge capacity of as large as500 mAh/g.

In the above embodiments, explanation was made for the application to anonaqueous electrolyte battery utilizing a nonaqueous electrolyteprepared by dissolving an electrolyte in an organic solvent is used as anonaqueous electrolyte, it may be applied to a polymer battery (polymersolid electrolyte battery) using a solid electrolyte.

As described above, according to the second aspect of the presentinvention, by using sulfur as a positive electrode active material, itbecomes possible to form a nonaqueous electrolyte battery with safetyand a large capacity using calcium as an ion conductive medium.

1. A nonaqueous electrolyte battery comprising a positive electrodeincluding carbon fluoride as an active material, a negative electrodeincluding calcium as an active material, and an electrolyte including animide salt of calcium or a sulfonic acid salt of calcium.
 2. Thenonaqueous electrolyte battery according to claim 1, wherein the imidesalt of calcium is a sulfonyl imide salt of calcium.
 3. The nonaqueouselectrolyte battery according to claim 2, wherein sulfonyl imide salt ofcalcium is an alkylsulfonyl imide salt of calcium.
 4. The nonaqueouselectrolyte battery according to claim 3, wherein the electrolyteincludes calcium bis(trifluoromethylsulfonyl)imide, Ca[N(CF₃SO₂)₂]₂. 5.The nonaqueous electrolyte battery according to claim 1, wherein thesulfonic acid salt of calcium is an alkylsulfonic acid salt of calcium.6. The nonaqueous electrolyte battery according to claim 5, wherein thealkylsulfonic acid salt of calcium is calcium trifluoromethanesulfonate,Ca(CF₃SO₃)₂.